Various types of devices are useful to disassociate selected substances from moving streams of fluid, gaseous or liquid, by which they are being carried. Filters and catalytic converters are examples of such devices, toward which the present invention is directed. Filters, for example, may be used to treat exhaust discharges from furnaces, internal combustion engines, or other combustion sources, which contain substances in particulate form. The offensiveness and harmfulness of discharging them into the atmosphere are well known. Such substances may be in the form of liquids and/or solids suspended in a gas (in which case, they are generally classified as "aerosols") or in a liquid, and may be relatively small in size. Although the features of the present invention can be beneficial in many, of not all substance separation applications, they can be particularly advantageous when applied to such fields as those of filters, catalytic converters, odor suppressors, toxic constituent removal devices, and the like.
Typically, such devices are housed in some kind of chamber, which optionally may be a closed container through which the fluid that is to be processed passes. Having entered a filter element, for example, the fluid stream is caused to pass through filtration media, in and/or by which solid and/or liquid particles or other constituents being transported by the fluid are retained. Retention may be by mechanical entrapment by the filtration medium of the particles that are to be filtered out. In that case, the size of the material filtered out will be a function of the size of the pores or passageways through which the fluid can pass. With some filtrates, processing principles other than mechanical entrapment may be utilized. For example, some aerosols, such as the exhaust from a diesel engine, include comparatively large amounts of fine, particulate matter, liquid as well as solid, in suspension. Such suspended matter tends to stick to surfaces with which it comes into contact. Thus, filters for such applications, in addition or alternatively to mechanical entrapment, may be made capable of retaining desired substances from the fluid stream by providing contact surfaces to which such substances may adhere, and by enhancing the accessibility of those surfaces to the fluid. To that end, relatively long passageways may be provided by which, for the most part, fluid passes through, rather than transverse to, the separation medium. In a unit containing fibrous separation material, for example, such passageways may be made to be substantially parallel to the general axial orientation of the constituent fibers. Either process and the structures adapted therefor, as well as still other devices, may also provide means for causing separation of desired constituents through chemical reactions, as by coating the surface of the filtration or other separation material with reactive substances, as in the case of odor suppressors and catalytic converters.
The separation of substances from very hot fluids, particularly those bearing a proportionally high fraction of fine matter, can also impose limitations on the physical properties of the separation materials. There have also been various attempts to produce suitable devices which may be cleaned for reuse so as to extend their useful life, for example, by "back-flushing" or the combustion of materials they have entrapped. This may occur at temperatures which are much higher than those encountered by the device in operation. Constituent materials that are suitable for such thermal environments may be difficult to form and retain in a shape or configuration that renders them capable of performing their desired separation functions. Thus, ceramic materials, while desirable in some circumstances because of their heat and chemical tolerance, have presented limitations as to how they could be formed into separation bodies. While they are susceptible to being formed into monolithic, solid bodies, they are inherently brittle and otherwise liable to break or deteriorate under physical stresses of the type regularly encountered in use. Other factors, such as the necessity to machine or die form in order to produce desired shapes, have added to these objections. Some materials, such as ceramic fibrous yarns or felt-like sheets, are tolerant thermally of the range of temperatures encountered in such applications and are capable of being formed more easily into desired shapes. Similar limitations also apply with respect to separation devices that are used in other treatments of fluid carrier media. For example, a catalytic converter typically may be exposed to a stream of hot gas or other fluid, as may also devices for deodorizing fluids. Even though some such applications do not involve very high temperatures, high efficiency and volume capability, with assurance that virtually all of the material passing through the device will be effectively treated, are desired characteristics which they have in common with devices of the type herein before described, and therefore they present many of the same problems. Further, the operation of devices at elevated temperatures and/or in chemically aggressive environments frequently requires that the separation media be used efficiently to minimize the cost of the filter.
Accordingly, it is an object of this invention to produce fluid treatment devices that are capable of removing desired substances from suspension in fluids, liquid as well as gaseous.
Still another object of this invention is to produce devices that satisfy one or more of the other objectives set forth herein and are tolerant of comparatively high temperatures.
Yet another object of this invention is to produce devices that satisfy one or more of the other objectives set forth herein and may be easily formed into desired shapes.
A further object of this invention is to produce devices that satisfy one or more of the other objectives set forth herein and have high flow-through volume capabilities.
Another object of this invention is to produce devices that satisfy one or more of the other objectives set forth herein and exhibit structural stability and durability in a wide variety of environments.
Yet another object of this invention is to produce devices that satisfy one or more of the other objectives set forth herein and are adapted for regulating the flow of fluid therethrough as between being transverse to the constituent separation material, or along elongated travel paths therethrough.
Still another object of this invention is to produce devices that satisfy one or more of the other objectives set forth herein and exhibit structural stability and durability in a wide variety of environments.
Another object of this invention is to produce devices that satisfy one or more of the other objectives set forth herein and make use of a high percentage of the separation media.
Still another object of this invention is to produce devices that satisfy one or more of the other objectives set forth herein and minimize the pressure drop of the fluid in passing through the device.